The present invention relates to a pneumatic tire more particularly to a structure of a sidewall portion of the tire capable of hiding bulges or dents occurred in the outer surface of the sidewall portion and deteriorating the appearance of the tire.
Usually, a pneumatic tire is manufactured by wrapping or winding various components such as strips of rubber and strips of rubberized reinforcing cords.
In recent years, on the other hand, there is a trend toward light weight tires from the aspect of low-fuel consumption and resource saving. Therefore, the thickness of the sidewall rubber covering the carcass ply cords becomes reduced when compared to before. As a result, in the outer surface of the vulcanized tire, especially, the outer surface of the tire sidewall portion, bulges or dents due to a turnup portion of a carcass ply, an overlap joint between circumferential ends of a wound strip and the like are more noticeable. Thus, there is a problem with the external appearance of the tire.
In Japanese Patent Application Publication Nos. JP-A-2009-143488 and JP-A-2003-182317, there is disclosed a tire sidewall portion provided in the outer surface with a serrated zone (b) formed by a large number of serration ridges (a) which are arranged circumferentially of the tire at regular intervals so that the serration ridges (a) extend radially at a constant angle with respect the radial direction as shown in FIG. 11. (in FIG. 11, the angle is zero) Taking a partial view of such a serrated zone (b), the serration ridges (a) are parallel each other.
If a bulge or dent is occurred in such a serrated zone (b), the selection pattern which is originally uniform, is disturbed. Therefore, the existence of the bulge or dent becomes rather remarkable contrary to expectations.